Homes insulated with fiberglass batts are leakier than homes insulated with cellulose or spray polyurethane foam. Until recently, fiberglass batt manufacturers shrugged off the damning air-leakage data, insisting that their batts could deliver the R-value promised on the packaging — and then changed the subject.
In recent years, however, manufacturers of fiberglass batts have begun facing up to their product’s Achilles’ heel — the fact that fiberglass batts are so air-permeable that they usually perform poorly. Worried that competing products are beginning to gain market share, batt manufacturers are finally addressing air infiltration.
A new kind of goop
Two leading fiberglass manufacturers, Owens Corning and Knauf, have developed similar air-sealing products that are best described as sprayable caulk. The Owens Corning product is called EnergyComplete, while the Knauf produce is called EcoSeal. When installed to seal leaks in wall assemblies, floor assemblies, and ceiling assemblies, these sprayable caulks improve the performance of air-permeable insulations like fiberglass batts or blown-in fiberglass.
Here’s how the systems work: an insulation contractor takes a high-pressure spray rig and sprays goop to seal leaks in stud bays and other framing bays. Once the sprayable caulk has cured, the cavities can be filled with batts or blown-in fiberglass.
It’s not flash-and-batt
To many builders, these systems sound like a variation on flash-and-batt (a system combining spray polyurethane foam and fiberglass batts). But sprayable caulk should not be confused with spray foam. A flash-and-batt job requires the installation of a 2-inch-thick layer of closed-cell spray foam on the interior side of the wall sheathing; the foam layer has a measurable R-value.
EnergyComplete and EcoSeal are different; they aren’t supposed to provide any R-value. Instead of installing a layer of foam that covers the sheathing completely, these products are used to seal the edges of each stud…